As the method of making regenerated collagen fiber light in color and water-resistant, JP-A-4-50370, JP-A-6-173161 and JP-A-4-308221 disclose the method for treating collagen fiber with metallic salt such as aluminum salt or zirconium salt and JP-A-4-352804 and JP-A-2000-199176 disclose the method for treating collagen fiber with an epoxy compound. As the method for shaping regenerated collagen fiber, JP-A-4-333660 and JP-A-9-250081 disclose the method which comprises moisturizing the fiber in warm water or an aqueous solution containing monovalent or divalent cationic hydrosulfate and heat-treating the fiber. However, when regenerated collagen fiber made water-resistant by treatment with metallic salt such as aluminum salt or zirconium salt is shaped according to the above method, though shape can be given to the fiber, the ability to maintain the shape (set property) is extremely low. Furthermore, the given shape is lost immediately when washing (including shampoo) and drying are repeated. Thus, using the fiber for hair products such as wigs, hairpieces and doll hair was difficult. Also, uncolored fiber can be obtained by using formaldehyde, but in this case the shaping property of the fiber was not satisfactory. Additionally, when using polyol of glycidyl ether which is regarded to be the most preferable among the epoxy compounds described in JP-A-4-352804, the fiber became brittle and hard and the strength was decreased significantly. Also, problems tend to occur during the process of producing hair ornaments such as implanting hair or operating a sewing machine and the shaping property was not satisfactory.
Furthermore, in the water-insolubilizing reaction of collagen fiber by epoxy compounds disclosed in JP-A-4-352804 and JP-A-2000-199176, when the reaction solution is set to a high pH range in order to reduce the reaction time, the hydrolyzing reaction of the collagen peptide bond advances and obtaining fiber of the desired properties tends to be difficult (deterioration of touch of hair in wet conditions and decline in set ability). As a result, epoxy compound treatment of collagen fiber is preferably conducted under a pH range in which the reaction rate of the epoxy compound and collagen is relatively slow, in order to control the hydrolyzing reaction of the peptide bond. Therefore, this step requires a great deal of time for the collagen fiber to be sufficiently water-insolubilized and is also unsatisfactory as capital investment inflates and productivity decreases.
The object of the present invention is to provide regenerated collagen fiber with light color and excellent touch in wet conditions, which can easily be formed into the desired shape, be set and firmly maintain the shape. The present invention also aims to reduce the treatment time of regenerated collagen fiber by a monofunctional epoxy compound and to improve productivity thereof.